Increased walnut yields with brassinosteroid application

Abstract

Methods and materials for producing walnuts with improved characteristics including: increased whole nut size, kernel size, shell size and hull size, and increased fruit set are disclosed. Treatments with 28-homobrassinolide (HBR) and in some cases, HBR with forchlorofenuron (CPPU), increase walnut whole nut size, kernel size, shell size, hull size, and fruit set in Serr and Chandler walnuts. Additionally HBR affects the pollen tube growth rate and germination percentages which may relate to increased fruit set and size. Presumably the increases are related to the effect of HBR on pollen load, and possibly also with embryonic development and stimulation of cell division. These results can be generalized to additional PGRs: epi-BL, CA, and HCS and mixtures thereof with CPPU. Increase in fruit set or seed size are both factors that directly correspond to higher yields; making these PGRs effective treatments for increasing walnut crop yield and ultimately walnut crop profitability.

1 . A solution for increasing the mass of edible seeds from a walnut tree comprising a plant growth regulator selected from the group consisting of 28-Homobrassinolide, Brassinolide, 24-epibrassinolide, Gibberellic acid, Castasterone, and 28-Homocastasterone. 
     
     
         2 . The solution of  claim 1  further comprising forchlorfenuron. 
     
     
         3 . The solution of  claim 1  in which the concentration the plant growth regulator is between approximately 0.4 ppm and 20 ppm. 
     
     
         4 . The solution of  claim 1  further comprising approximately 10 ppm forchlorfenuron. 
     
     
         5 . A method for increasing the mass of edible seeds harvested from a walnut tree comprising the steps of applying a aqueous solution of a plant growth regulator selected from the group consisting of Homobrassinolide, Brassinolide, Epibrassinolide, Gibberellic acid, Castasterone, and Homocastasterone to the flowers of a walnut tree at a determined time during flowering. 
     
     
         6 . The method of  claim 5  in which the aqueous solution is comprised of between 0.4 ppm and 20 ppm Homobrassinolide. 
     
     
         7 . The method of  claim 5  further comprising the steps of preparing said plant growth regulator solution by diluting a concentrated plant growth regulator solution to the desired final concentration, allowing the edible seeds to grow to maturity following application of the aqueous plant growth regulator solution, and harvesting the mature nuts. 
     
     
         8 . The method of  claim 5  in which the determined time during flowering is the pre-bloom growth stage. 
     
     
         9 . The method of  claim 5  in which the determined time during flowering is the full-bloom growth stage. 
     
     
         10 . The method of  claim 5  in which the determined time during flowering is the post-bloom growth stage. 
     
     
         11 . The method of  claim 5  in which the aqueous solution further comprises 10 ppm forchlorfenuron.